Automatic scale for copying cameras



BEST AVNLABLE CDP\ J. VERBURG AUTOMATIC SCALE" FOR COPYING CAMERAS Filed March 23I 1925 2 Sheets-Sheet 1 ATTORNEY BEST AVALABLE COPE April 6 y 1926.

J. VERBURG AUTOMATIC SCALE FOR COPYING CAMERAS Filed Marchs 1925 2 Sheets-Sheet '3 Zia-F my Nu R E m IcA \Mw BEST VlLBL CCPE Patented Apr. 6,' 1.926.

JOHN'VERBUBG, 0F JAMAICA JUNCTION, NEW YORK.

ATOMLATIC SCALE FOR COPYING CAMERAS.

Application iiled March 23, 1925. Serial No. 17,497.

To all wko-m it may concern:

Be it known that I, JOHN VERBURG, a citizen of the United States of America, residing at Jamaica Junction, county of Queens, State of New York, have invented certain new and usefulA Improvements in Automatic Scales for Copying Cameras, of which the following is a specification.

My invention relates to theart of makl ing reduced or enlarged photographic copies of any given design, photograph or object, and comprises a simple device for instantly determining the camera adjustments Vnecessary to produce a given result without making the somewhat complicated calculations -heretofore required, or hunting them up in a previouslyv computed table. My invention 7also has the advantage of readily giving the 'adjustments necessary for any unusual reduction 'or enlargement ratio which may n'otljepgi'ven in the standard tables.

InA the adjustment of a camera for makin U' such copies at a given reduced or enlarged .size V'necessary to place the lens at a 5 cvertainfl-distance from the photographic plate or hlm, which distance is usually called the bellows adjustment fand then to place thelcop'ykatia'corresponding par ticular distance from the lens. The present invention comprises a simple apparatus by which these required distances can be automatically determined in inches, or other linear units, marked on scales thereon, and

the work `of the photographer thereby be rendered more rapid and accurate. The best form of apparatus at present known to me embodying my invention, together with sundry modifications thereof, are illustrated in the accompanying two sheets of drawings, in which, .Y y u Fig. l is a plan of the preferred form of apparatus.

Fig. 2' is a side elevation thereof.

-Fig. 3 is a perspective detail of the adjustable pin, the position of which corresponds' (Fig. 1) having astraight, undercut groove 2, near one edge, in which groove slides the block 3 having Haring sides to tit groove 2. Qn this block a swingingA straight edge 4 1s pivoted at 5, which straight edge may be clamped in any position on said block by means of clam ing screw 7 set in the block and passing It roughv curved groove 6 in said straight edge.

9 is a scale parallel to slot 2, and 10 another scale at right angles to the first mentioned one. The divisions on these may be on any convenient scale, say sixteen to the inch, and are measured and numbered from the vertex 8 of the right angle formed by the scales. 11 and 12 are scales parallel respectively to 9 and 10, the main divisions on which may be on a larger scale for convenience, say four to the inch, and are simi larly numbered and measured from the vertex of the right angle formed by 11 and 12.

A second undercut slot 13 bisects the angle formed by scales 9 and 10, andylli is a block having Haring sides fitting in groove or slot 13 and adjustable in any position therein. 15 is a knife-edged pin set in one end of block 14, and 17 is ascrew threaded pin set near the other end and carrying thumb screw 16 and loose washer 18. When thumb screw 16 is turned to the right itis forced down on washer 18 which overlaps the edges of groove l13, the block 14 is wedged up against the undercut edges of the groove and clamped in the position then occupied.

19 is a cross mark on the upper face of block 14 and 20 a scale along the edge of slot 13 cooperating with mark 19. The divisions on scale 20 are s'o located and numbered that when mark 19 Iis opposite any one of them the knife-edge of pin 15 will be in a positionsuchv thatif a line be drawn from it perpendicular to either scale 9 or 10, it will cut the same at a division corresponding in number to that graduation in scale 20 opposite to the mark 19. This means, of course, that the graduation mark on scale 20 opposite mark 19 will indicate the distance from vertex S at which the.perpendicular 15, 15, or 15, 15b, cuts scale 9 or 10, and also the length of these perpendiculars, to the upper edges of these scales since 15, 15, 8. 15b is a. square.

Fig. -i shows in diagram a camera with a casing 2l at the back 22 of which is placed the photographic plate or film. 23 is the bellows carrying lens 24. The upright 25 1 it is shown .opposite division 20, the focal length of the lens 24 being assumed at that number of inches. The clamp screw 7 is then loosened and block 3 and straight edge 4 adjusted so that the upper edge of 4 will cross the edge of Scale 11 at a point where the reading thereon corresponds to a linear dimension of the copy to be used, and will cross the edge of scale 12 at a point where the reading corresponds to a similar linear dimension of the copy to be made, or size wanted. This is indicated inA full lines. The straight edge is then-clamped in this position and the block 3 slid along groove '2 until the straight edge bears against the imi-fe edo'e of pin l5, as indicated in dotted lines in Ifig. 1. The division at which the straight edge then cuts scale 9 will thereupon give the copydistance- XY, and that one at which the straightedge cuts scale 10 will give the bellows adjustment YZ.

The scales 11 and 12 may be used in a reverse manner, the copy size being measured ori-12 and the size wanted on 11, and in that case the readings must also be reversed on scales 9 and-10.v

Also one set of scales may be omitted and both sets of readings taken from one. A

simplified apparatus 'of this kind is illustrated in Fig. 5 Where the scale measurements are marked along adjacent two sides of the block 31, from a point'32 near one corner insany arbitrary but uniform unit-s subdivided into groups of four for convenience. The straight edge 33 is swiveled at 34 under arm 39 projecting from block The swivel bearing in the straight edge is offset so that the line of the straight edge passes through the pivot center. (See Fig. 5.) Block 35 slides in undercut slot 36 which bisects the right angle formed by the scales. The straight edge 33 is clamped in adjusted angular position on said arm 39 by thumb screw 37. The block 35 can lie clamped in any position in the slot. if desired, by the clamp screw 39a similar in arrangement to 16 in Fig. 1. and 39 are the scale markings along slot 36, which arc :trranged to cooperate with the rear edge 35 of block 35, or with any mark thereon corresponding to mark Q0 in Fig. l.

In operation the straight edge is :adjusted in full line position to cut the scales at polnts having group markings correspond- Leren-i1 BEST AVAlLABLE @GPX this position and block. 35vis then. slid along.

slot 36 until. its'rear. edge 35 is opposite the division in. scale 391 which corresponds to the focal'- l'engllrl of the-lens being -used. In Fig. 5 it isshown-opposite division'- 24, that being theV focal length aumed. Thesmaller scale divisions then cut by the straight edge will. give the copy distance and bellows adjustment as before. '0f

cour;'e the finer divisions ol' the scales could be used for adjustingl the angularity of straight edge, but usually` they are too minute for accurate adjustment of the straight edge, so the larger unit groups of:

four should" be-used. All. that is necezsary is that the straight edge shall.` be initially adjusted so that' the base andpenpendicular of the right-angled. trianglev formed by it with the scales shall have= the proportionsin lengthpvhiclr size ofi copy bears tosize wanted when" measured in the same unit,

whether large orsmall.

In thefurther -modi cation showin inl Fig.

6, the ,slidingililock mounting fori thestraight edge-isereplcedaby: apara'llel ruler' mounting. *Ira this modification er1-.may be a drawingfboardisupportingsleet' ofpaper' on which theriglit-arigledlscale, and-focalv distance points-474 are marked'injnk or. pen- I cil. The. straightedge42iis'1carred-by pivoted parallel lm'ls 43343;. romabas'e member 44, which, fins pivoted on; th Screw" 452 thisA thumb? isf" enedg. straight; edge 42 may# be' adjustedl to-A cut the-sc es-'ab'the pointsmarked bythe larger divisions representng. size ofcopy. and size wanted, asbefore; (rall as shown in u'll lines) The base-44istlien clhmped in the assumed: position: by" turning; thumbT screw 45, andtli'estraight edge'swung'back until it passesthrough-1 the'.1 dot: inl scale 47 representing the-focallengtlr the lens-.being-used, as indicated: in? dottedg. lines'-a focal lengthjof 2O being-assumed?? e points at which the straight. edgetlien= cuts the scale 46 willi'give-tiieI-copydistancefand bellows adjustment as before, the finer divisions 'again being' used? for this; embodiment of? my invention, the particular dot on thescale'-47sel'ected because it i'svtlie one located ata. distance from the scales corresponding tofthe focall'engthfof the particular lens used; is, in effect', a stop for the moving straight edge.

In all cases. the copy distance is always obtained from the scale on whiclit size of copy has been measured, or which is' parallvl to that on which said dimensionhas been measured, and the bellows adjustment is attained from the scale on `which the size wanted has been measured, or which is BEST VNLBLE @GFX parallelto that on which said last named dimension has been measured.

While a correct understanding of the geometric and optical laws in accordance with which my invention operates is not necessary for its successful use, I may say that, Aaccording to my present understanding, l believe the correctness of the readings obtainable from my improved apparatus to result from the embodiment of the following principles therein:

Referring to the diagram Fig. 7 it is generally understood in the art that if a camera lens L has a certain focal length YF and it is desired to reproduce a certain piece of copy having a linear dimension AB in a size having a corresponding linear dimension CD, in a given ratio thereto, the distances of copy and photographic plate from the plane of lens L are fixed by the following requirements:

Calling distance YX, the copy distance and the distance YZ the bellows adjustment7 (because the lens is usually mounted 5 on a bellows extension of the camera casing to give it adjustability in position), the first requirement is that,

1 YZ CDl(size wanted) -AB (size oi copy) The foregoing is true for all thin lenses, and, in the case of a combination of lenses in one camera it is understood that each of ..5 these distancesis measured from the plane of the outer lens on the nearest side.

Whenever such lens,`whether simple or compound, however, has a given fixed or adjusted length of focus, YF, there is a furer requirement that also FZ CD (2) FYAB Looking at the skeleton diagram of my scale, Fig. 8, it is obvious that if the straight edge SE is so adjusted in a dotted line position SE that it cuts the sides of the right angle XYZ.I at points A and D which are at distances from vertex Y respectively the same as the copy dimension AB and the size wanted dimension CD, and is then slid away from vertex Y, but during such motion of translation held always parallel to its original position,it will always, in any given position XZ' cut the sides of the right angle XYZ at points such that,

That is to say, any bellows adjustment YZ and copy distance YX pair, or set, of relative distances so determined by the 55 sliding straight edge will satisfy equation (l) above given. It remains only therefore to get that bellows adjustment and copy distance pair or set which will also satisfy equation (2), and this is done by locating a point F on the 45 degree line HY such 70 that when perpendiculars F F and F F are drawn to sides XY and YZ respectively. of the right angle, distances FY and FY will each equal the focal length YF (Fig. 7) and then moving straight edge SE to a position such that it fill pass through point F, as shown in full lines in this diagram, Fig. 8.

The fact that the copy distance XY then shown on the scale will bear the same` B0 ratio to bellows adjustment, YZ, as copy size, AB, bears to size wanted, CD, is obvious as previously explained. Also, as triangles F FZ and AYD are similar, it follows that, 35

3) ref/:mim

Then, since F F:F Y (F F F Y being a square) it follows that when F Y is substituted for F F in equation (3) the desired equation (fulfilling the second requirement) FZ CD (2) FYAB results That is to say, when the straight edge is moved into full line position SE, such that it passes throu point F, it will cut the lo sides of the rig t-angled scale at points X` and Z which will read on the scale in inches a copy distance (XY) and a bellows adjustment ZY which, with a lens havinga focal length FY, will reproduce the copy AB, in the size wanted, CD.

Perhaps still other for-ms of apparatus than those here shown could be developed which would operate on the principle of my invention as above explained and still be 110 within the scope thereof. The essential elements of those shown are: a right-angled scale or set of parallel scales, an angularly adjustable straight edge, means for moving said straight edge over said scale or scales without varying its initially adjusted angularity thereto, and means so locating said movable straight edge that it shall go through a point on the line bisecting the right angle which is distant from-the vertex of said angle a distance equal to the diagonal of a square having the lens focal length for its sides, or, to state this requirement in another way, the fixed point on the bisector of the right angle must be at a distance from the sides of the angle equal to the focal length of the lens being used.

Having described my invention, I claim:

l. An apparatus for determining the adjustments required for producing with a 30 BEST AVNLAEL @CPN given camera copies of given sizes which comprises, in combination, two similar rectilinear scales having a common zero point at the vertex cf a right angle formed by them, a straight edge angularly adjustable with reference to said Scales, a device permitting said straight edge to move over said scales without varying its angle of inclination thereto after adjustment, and means for determining that position of said movable straight edge at which it will cross a line bisecting the angle formed by said scales at a point removed from each of said scales by a distance corresponding with the focal length of the camera lens.

2. A combination such asset forth in claim 1 in which said means for determining the.

3. An apparatus for determining the adjustments required for producing with a given camera copies of given sizes which comprises, in combination, two similar rectilinear scales having a common'zero poit at the vertex of a right angle formed by them, a straight edge angularly adjustable with reference to said scales, a device permitting said straight edge to move over said scales Without varying its angle of inclination thereto, and means for so adjusting the position of said straight edge Without varying its inclination that it will *ouch a point on the bisector of said angle located at a distancefrom the sides thereof equal to the focal length of the camera lens, said means comprising an adjustable pin adapted to be placed at the said point which indi- Cates the focal length of the lens.

JOHN VERBURG. 

